The present invention relates in general to an improved planing watercraft hull and more particularly to a hull adapted for use with a small, easily transportable waterjet propelled watercraft.
Personal watercraft currently enjoy widespread popularity due to their ease of use and affordability. These watercraft typically employ an internal combustion engine coupled with a waterjet propulsion system oriented below the level of a seat for accommodating a rider as generally described in U.S. Pat. No. 5,584,733 to Kobayashi, incorporated herein by reference. Other personal watercraft are intended for use by a standing or kneeling rider. All of these watercraft are heavy in weight and require a trailer or other means for transporting the watercraft to the water, where the trailer and watercraft descend a boat ramp to enable the watercraft to access the water. In addition, the large size and heavy weight of these watercraft necessitate large amounts of horsepower to enable the watercraft to achieve the speed required to attain an optimum planing orientation and performance.
Planing-type hulls are well-known and commonly incorporated in the design of watercraft. The primary advantage provided by a planing-type hull over hulls of other design, such as displacement-type hulls found in canoes and kayaks and the like, is that a planing-type hull rises out of the water vertically as the horizontal speed of the watercraft increases, reducing the volume of the hull that is submerged thereby reducing drag and permitting higher speeds. The primary drawback of planing-type hulls, particularly with respect to many of the narrower hulls of the type found in contemporary personal watercraft, is the lack of stability when travelling in a straight line. This problem is exacerbated in rough waters. When such planing-type hulls are powered by means of water-jet propulsion, the tendency of the transom to rise with increasing speed combined with rough waters inevitably results in a loss of power and control as the jet pump intake loses contact with the water.
Watercraft of the prior art have sought by various methods and designs to solve the control problem inherent in jet-powered watercraft having planing-type hulls. U.S. Pat. No. 4,004,542 to Holmes, incorporated herein by reference, is directed to a boat for use with a waterjet propulsion unit incorporating a planing hull having a generally V-shaped bottom with a depending flat-bottomed support pod and stabilizing strakes. U.S. Pat. No. 3,911,846 to England, incorporated herein by reference, is directed to a shallow draft boat hull for use with a waterjet propulsion unit, said hull comprising an elongate step extending longitudinally of the bottom along the keel forwardly from the transom. These prior art arrangements sought to improve straight ahead stability but at the cost of speed due to the increased resistance with the water surface of the structures depending from the hull.
In addition, waterjet powered personal watercraft currently almost uniformly employ a two-stroke engine because of the high horsepower output provided by the two-stroke engine. However, two-stroke engines contribute high levels of pollution to waterways, especially when used in tandem with an exhaust system which injects exhaust directly into the water. The use of a four stroke engine minimizes water pollution compared to two-stroke engines used in the majority of watercraft. In conventional watercraft employing a two-stroke marine engine, between 25 and 35 percent of all of the gasoline in the tank is discharged through the tailpipe unburned and directly into the waterway because water is drawn into the engine for cooling and then mixed with exhaust and expelled. The design of the two-stroke engine allows unburned fuel to enter the cylinder at the same time the burned residue from the previous stroke is expelled from the engine. In addition, in a two-stroke engine lubricating motor oil mixes with gasoline, and as a result the expelled unburned gasoline contains heavier, non-evaporating motor oils. A four-stroke engine, on the other hand, has a dedicated combustion and exhaust stroke, substantially eliminating the problem of escaping unburned fuel. The use in the present invention of a four-stroke engine in combination with an exhaust system which expels exhaust into the air therefore represents an improvement over personal watercraft of the prior art.
Accordingly, it is a principal object of the present invention to provide an improved hull for a watercraft having stability while stationary and at low speed as well as stability and minimal water resistance when travelling at high speed straight ahead.
It is yet another object of the present invention to provide an improved hull which reduces the structural stress concentration within the hull and provides an efficient means for removal of water that otherwise would create secondary drag.
It is another object of the present invention to provide an improved hull for a watercraft which facilitates boarding of the watercraft from the water; particularly deep water.
It is another object of the present invention to provide a lightweight waterjet powered watercraft having an improved hull.
It is still another object of the present invention to provide a waterjet powered water craft with a removable power source so that the watercraft may be carried by a single person and transported without the need of a trailer.
It is yet another object of the present invention to provide an improved hull which minimizes weight bias balance problems.
It is still another object of the present invention to provide an improved exhaust system for a watercraft comprising the improved hull.
It is still another object of the present invention to provide an improved waterjet pump system for a watercraft comprising the improved hull.
It is a still further object of the present invention to provide an environmentally friendly power supply for a watercraft comprising the improved hull.
These and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended Claims.